As rubbers for a tire tread, rubbers having a high frictional force have been sought from the viewpoint of safety. On the other hand, a tire having a small rolling resistance, that is, rubbers having a small hysteresis loss at the time of tire rolling have been sought from the viewpoint of the environment and health. To achieve both of these performances, the technology for compounding silica is known (for example, see Journal of the Adhesion Society of Japan, Vol. 37, No. 5 (2001), pp. 21 to 26). As the reason why silica exhibits such a characteristic, the fact that a silica-containing rubber has a low modulus of elasticity at the low strain region may be mentioned. However, since silica has to be chemically bonded with rubber using a silane coupling agent, the reaction between the silica and the silane coupling agent has to be controlled. In particular, there is a problem that restrictions arise in processing when compounding a large amount of silica.